Microphone Amplifier BA7760 / BA7760F. Multimedia ICs

Transcription

1 Microphone Amplifier The BA0 and BA0F are dual microphone amplifiers designed for audio signal amplification. These are low noise amplifiers with a low -dbv (typically) equivalent input noise voltage. Each IC has an internal mixer buffer amplifier for the mixing of signals from two channels. When used with the BAS or BAFS, the BAAS or BAAFS and BU9S or BU9F, these ICs simplify the configuration of digital echo systems with two inputs (for karaoke duets, for instance). Applications Audio equipment with karaoke features, VCRs, LDs, etc. Features ) Internal -channel low noise microphone amplifier. ) Internal mixer buffer amplifier with mute function. ) Available in types of packages: DIP -pin or SOP -pin. Absolute maximum ratings (Ta = C) Parameter Symbol Limits Unit Applied voltage V Power BA0 00 Pd dissipation BA0F 0 mw Operating temperature Topr ~ C Storage temperature Tstg ~ C Unmounted. Reduced by.0mw for each increase in Ta of C over C. Unmounted. Reduced by.mw for each increase in Ta of C over C. Recommended operating conditions Parameter Symbol Limits Unit Power supply voltage ~ V

2 Block diagram MIX BF 9 0 MIX OUT MUTE CTRL MIX IN MIC OUT Ch FILTER Ch MIC IN Ch ( ) MIC IN Ch ( ) GND RIPPLE FILTER MIC AMP CH MIC AMP CH MIC OUT Ch FILTER Ch MIC IN Ch ( ) MIC IN Ch ( ) Pin descriptions Pin No. Pin name RIPPLE FILTER Ripple filter Function Pin type Base (NPN) // kω GND GND MIC IN ( ) Ch CH microphone amplifier input ( ) Base (NPN) // 0kΩ MIC IN ( ) Ch CH microphone amplifier input ( ) Base (NPN) FILTER Ch CH microphone amplifier fc Base (NPN) ~ 0Ω MIC OUT Ch CH microphone amplifier output Push-pull MIX IN Mixer buffer input Base (NPN) // kω MIX OUT Mixer buffer output Push-pull 9 MIC OUT Ch CH microphone amplifier output Push-pull 0 FILTER Ch CH microphone amplifier fc Base (NPN) ~ 0Ω MIC IN ( ) Ch CH microphone amplifier input ( ) Base (NPN) MIC IN ( ) Ch CH microphone amplifier input ( ) Base (NPN) // 0kΩ MUTE CTRL Mute control Fig. Parallel and series respectively refer to parallel and series insertion. All figures are standard values.

3 Input / output circuits MUTE CTRL 0kΩ Fig. Electrical characteristics (unless otherwise noted, Vcc = V, Ta = C) Parameter Symbol Min. Typ. Max. Unit Conditions Supply current Iq...09 ma MIC AMP (GVC = db, f = khz) Open loop voltage gain GVOM.0.0 db VIN = 0dBV Input conversion noise VnM dbv Rg =, DIN AUDIO Distortion Maximum output level Input impedance Crosstalk MIX BF (f = khz) Voltage gain Output residual noise Distortion Maximum output level Input impedance Mute level Mute threshold voltage THDM VomM ZinM CTM GVB VnB THDB VOMB ZinB MTB VTHMUTE % VIN = 0dBV. 0. dbv THD = % 9 kω VIN = 0dBV, 00kΩAttenuation dbv VIN = dbv Rg =, DIN AUDIO db VIN = 0dBV 0 00 dbv Rg =, DIN AUDIO %. 0. dbv VIN = 0dBV THD = % 0.0. kω VIN = 0dBV, 0kΩAttenuation 0 00 dbv VIN = 0dBV, DIN AUDIO... V

4 Measurement circuit MIC IN MIC OUT MIX OUT Ch 0µF Ch µf 0kΩ kω 0µF MΩ.9kΩ 0pF.µF 9 0 MIC AMP Ch MIX BF MIC AMP Ch.µF kω 0pF.9kΩ MΩ.µF MIX IN 0µF µf MIC IN MIC OUT Ch Ch MUTE CTRL BA0 / F µf Fig. Circuit operation (Refer to Application Example ) The BA0 and BA0F are dual microphone amplifiers. The audio signals from the microphones are input to pins and. The gain at this time is determined by attached resistors R / R and R / R. By attaching capacitors to pins and 0, the microphone amplifiers can be given frequency characteristics like those shown below. (Note: The attached component numbers are those used in Application Example. ) VOLTAGE GAIN : GV (db) 0dB 0dB 0dB C = 0pF C = 0 PHASE 0dB 0 0dB 0 0 khz 0kHz 00kHz MHz 0MHz00MHz FREQUENCY : f (Hz) Characteristics when using standard components and standard constants Fig. Microphone amplifier frequency characteristics

5 Output from these dual amplifiers is level-adjusted with an attached volume control (VR) and then input to pin and mixed by the mixer buffer amplifier. The ON / OFF operation of the mixer buffer amplifier can be controlled with the signal input to pin (MUTE CTRL). For DC loads, this volume control (VR) should be set above.kω to assure proper performance of the IC s internal driver. Mode Control signal Operation MUTE L Muted MUTE H Normal operation Application example MIXOUT 0kΩ 0µF MIX BF kω kω 0.µF 0.µF kω (VR) µf kω 0pF 9 0 R MIC AMP Ch MIC AMP Ch 0pF R kω µf kω (VR) µf R R µf.µf MICIN Ch.µF MICIN Ch MUTE CTRL BA0 / F µf Fig.

6 External dimensions (Units: mm) BA0 9. ± 0. BA0F. ± 0.. ± 0.. ± 0. 0.Min.. DIP. ± ± ~ 0. ± 0.. ± 0.. ± ± ± 0. 0.Min. SOP 0. ± 0. 0.